1. Field of the Invention
The present invention relates to improved methods and associated apparatus for conversion of agricultural waste to a liquid fuel and, more specifically, it relates to such conversion processes and associated apparatus which will facilitate economical on-site conversion.
2. Description of the Prior Art
Both energy needs and environmental considerations have resulted in many efforts over many decades to provide alternative sources of fuel which would satisfy both objectives. To date, in addition to the conventional fossil fuel sources and the use of nuclear energy, numerous approaches have been taken, including, for example, unique energy sources, such as the wind, or mechanical or thermal use of large bodies of water. Also, with respect to environmental considerations, focus on use of low sulfur coal and/or means for cleaning exhaust from such uses as utilities have been known.
The U.S. Department of Energy is faced with the immense task of balancing energy demand of our society with environmental consequences of generating that energy. The primary focus has been on the efficiency of conversion of fuel to a useful form of energy. Energy can simply be defined as the ability to do work. The energy value of a fuel normally is measured by temperature change and fundamentally fuels are valued by their ability to supply heat. In the traditional sense, some combustion process produces heat from the fuel. As fuel is oxidized, heat is released. The heat is converted through some mechanical means to a more useful form for application to society. The greater the efficiency of that conversion the more energy efficient we become and the less impact on the environment.
It has been suggested to convert agricultural and biological waste such as sawdust and various manures to liquid fuels and subsequently to energy (see Stiller et al., Fuel Processing Technology 49, 167, 1996 and Dadyburjor et al., Paper presented at 209th National Meeting, American Chemical Society, Anaheim, Calif., April, 1995). The project investigated the effects of recycling “waste” materials by using them as co-liquefaction agents for the conversion of coal to liquid fuels has been considered. See, for example the used shredded tires (see Sharma et al., Energy and Fuels 12, 589, 1998), plastic materials, such as polyvinyl chloride, (see Zondlo, J. W., Paper presented at 214th National Meeting, American Chemical Society, Las Vegas, Nev., September, 1997) and high density polyethylene, (see Dadyburjor, D. B., Paper presented at the Tri-State Catalysis Society Spring Symposium, Charleston, W.Va., April, 1998), as well as the ag- and bio-wastes.
In an effort to improve the coal liquefaction process, it was hypothesized that organics with conjugated double bonds that are plentiful in manures and other agricultural wastes would catalyze coal liquefaction reactions. In testing the hypothesis, it was found that the wastes did not improve the conversion of coal to liquid fuel, but the organic matter of the wastes were converted completely to fuel.
Coal is not a necessary prerequisite for fuel production from manures. Stiller et al., Co-processing of Agricultural and Biomass Waste With Coal, Fuel Processing Technology, In Press, 1996 indicates that one can produce fuel with good yields using the manure alone, along with an iron-based catalyst, and then the manure can be done almost independent of the manure source.
The present invention focuses on the use of agricultural waste, such as animal manure, for example, as a source of material from which to produce liquid fuel. (See, Stiller et al., Fuel Processing Technology 49, 167, 1996.)